Analysis of Lithium Battery Charging Principle

Lithium battery charging principle analysis Lithium battery charging process can be divided into four stages: trickle charging (low-voltage precharge), constant current charging, constant voltage charging and charging connection. The basic requirement of a lithium battery charger is a specific charging current and charging voltage to ensure the safe charging of the battery. The purpose of adding other charging auxiliary functions is to improve battery life and simplify the operation of the charger, including trickle charging of over-discharged batteries, battery voltage detection, input current restriction, turning off the charger after charging, and charging after partial discharge. The first stage: trickle charge. Trickle charge is used to pre-charge (recycle charge) the fully discharged battery cells. When the battery voltage is lower than about 3V, trickle charging is used. The trickle charging current is one-tenth of the constant current charging current, which is 0.1c (for example, the constant current charging current is 1A, and the trickle charging current is 100mA). The second stage: constant current charging. When the battery voltage is higher than the trickle charging threshold, the forward charging current performs constant current charging. The current for constant current charging is between 0.2c and 1.0c. The battery voltage gradually increases with the constant current charging process. In general, the voltage of a single battery is set to 3.0-4.2v. The third stage: constant voltage charging. When the battery voltage rises to 4.2v, the constant current charging is completed, and the initial constant voltage charging stage is completed. According to the fullness of the cells, the current gradually decreases from the maximum value during the charging process. When the current drops to 0.01C, the charging is considered to be continuous. (C is a way to indicate the nominal capacity of the battery to the current. For example, the capacity of the battery is 1000mAh, and 1C is the charging current 1000mA.) The fourth stage: charging connection There are two typical charging connection methods: use the minimum charging current to identify Or use a timer (possibly a combination of the two). The minimum current method monitors the charging current in the constant voltage charging stage, and continues charging when the charging current drops to 0.02~0.07c. The second method starts from the constant voltage initial charging stage and continues charging after 2 hours of continuous charging. With the above four-stage charging method, the charging time after the battery is fully discharged is about 2.5 to 3 hours. High-end chargers also use more safety methods. For example, if the battery temperature exceeds a specified window (typically 0°C to 45°C), charging will be suspended. After charging, if the battery voltage is detected to be lower than 3.89v, the charging starts from zero. The working process of the mobile phone charger is generally as follows: test the battery voltage, assuming that the voltage is lower than the threshold, then perform trickle charging; 2.2. When the battery is charged to a certain voltage (generally set to 2.9v), perform full current charging; 3. When When the battery voltage reaches the preset voltage (the lithium battery is generally 4.2v), the initial constant voltage charging is performed, and the charging current decreases at the same time; 4. When the current gradually decreases to the specified value, the charging process ends. When the battery voltage is lower than 2.5v (Vshort), the lithium battery charger uses 25mA current for pre-charging to prevent the lithium battery from deep discharge damage or even attack risk during fast charging. Charge the battery with a low voltage. When the battery voltage is lower than 2.5v (Vshort), the lithium battery charger will use 25mA current for pre-charging to prevent the deep-discharge lithium battery from being damaged or even attacked during fast charging. In addition to voltage detection, other auxiliary methods should be selected as a backup method to prevent excessive charges, such as battery temperature monitoring, battery temperature detection, and battery pack temperature sensors for continuous detection of battery temperature. When the battery temperature exceeds the set plan, the battery charging is turned off. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.